Gas turbine engines typically include a compressor for compressing a working fluid, such as air. The compressed air is injected into a combustor which beats the fluid, and the fluid is then expanded through a turbine. The compressor typically includes a low pressure compressor and a high pressure compressor.
The output of known gas turbine engines may be limited by the temperature of the working fluid at the output of the high pressure compressor, sometimes referred to as "T3", and by the temperature of the working fluid in the combustor outlet, sometimes referred to as "T41". To provide increased power output and cycle thermal efficiency without exceeding the T3 and T41 temperature limits, it is known to use an intercooler positioned in the fluid flow path between the low pressure compressor and the high pressure compressor.
Known intercoolers generally require the extraction and reintroduction of the entire gas turbine mainstream flow from and into the main gas turbine flowpath. Requiring that the entire gas turbine mainstream flow be extracted and reintroduced into the mainstream flow reduces the thermal efficiency of the cycle and adds component costs to an engine. Such intercoolers also introduce pressure losses associated with the removal of air, the actual cooling of that air, and ducting it back to the compressor. In addition, and in order to accommodate the entire mainstream flow, known intercoolers typically must have a large capacity. A significant amount of water is required by such high capacity intercoolers, and such high water consumption increases the operational costs. Of course, a larger capacity intercooler is more expensive, both to fabricate and operate, than a typical smaller capacity intercooler.
Also, it would be desirable to provide intercooling yet eliminate the requirement that the entire mainstream flow be extracted and reintroduced into the main gas turbine flow. It also would be desirable to reduce the required capacity for an intercooler yet provide substantially the same operational results.